Servomotor



R. H. HILL Dec. 25, 1945.

SERVO MOTOR Filed June 2, 1943 4 Sheets-Sheet 1 Dec. 25, 1945. R. H. HILL 2,391,702

' SERVO MOTOR Filed June 2, 1943 4 Sheets-Sheet 2 I I Z I %42 4344274 V n 24 [fin enfor- R. H. HILL Dec. 25, 1945.

SERVO MOTOR Filed June 2, 1943 4 Sheets-Sheet 3 llllllllllllllllllll Illlllll {'lilllllllllllll R. H. HILL Dec. 25, 1945.

SERVO MOTOR Filed June 2, 1943 4 Sheets-Sheet 4 Patented Dec. 25, 1945 UNITED "STAT ES 'SERVOMOTOR Robert'H. Hill, Detroit, Mich, assignorJto 'Genci-al Motors Corporation, Detroit, Mich.,;a .corporation of.Delaware Application 'JunefZ, 1943,, .SeriaIjNo. 89,397

'6 Claims.

This inventionrelates .to electric .servo .moltors 'foruse in systemsof electrical control.

It .is an object of this invention to provide .a servo. motor unit which is durable and compact andlightin weight and which includes an operating arm connectible with anapparatus to be controlled, a reversible electric motor and .speed reducing gearing driven bythe motor and connected with the operating arm. In on form of the invention, there i a friction clutch connecting the arm with the gearing, and there are limit switches connected directly with the arm. This provides for maintaining a fixed relation between the operating arm and the switches, this relation remaining undisturbed in case it'is desired to take over control of the operating arm by manual means.

Further objects and advantages of the present invention will be .apparent .from the following description reference being had to the .accompanying drawings wherein a preferred embodiment ofthe present invention is clearly shown.

'In the drawings:

.Fig. 1 is a front view of the unit embodying the present invention, this view being takenin.

Fig. 3 is a sectional view on linel3"3;ofFig. 1.

Fig. 4 is a sectional view on line 4-4 ofFig."3.

"Fig. 5 is a sectional view on line'5- 5 of Fig. 3.

Fig. "6 is a left side View of the speed reducer subassembly and is taken substantially .on the .line66Fig. 3.

Fig. '7 is a right side-view ofthe speed reducer assembly and is taken substantially on the line 1-1 of Fig. 3.

Fig. 8 is'a sectional view of the speed reducing gearing, the sections being taken on the axes of the shaft bearings.

Fig. 9 is a sectional view 'on line"99 of 3;

Fig. 10 i a sectionalview .on line l0-l0 of Fig. 3.

Fig. 11 is a view correspondingto 'Fig. .4 showing a modification of the unit shown inFigs. 3 and 4. This modification includes a centering switch as well as a limit switch, :the form shown in Fig. 4 providing only the 'limitswitch.

Fig. 12 is a sectional view taken generally on the line I2l2 of Fig, 11. and omits thefriction clutch shown inFig- 3.

'Fig. 13 is a view in the direction of arrow 13 of Fig. 12 showing. only the operating arm.

Fig. 14 is a wiring diagram showing the circuits of the motor and the limit and centering switches.

Referring to Fig. '3, the electric motor. 2000mprises a metal shell'2l supporting a laminated 'fie'ldirame i22 carrying .field windings. 23. Shell 2| carries a flange 24. attached-by -:rivets' 25.110 -an .end plate..26 carrying afball bearing 21. Shell 121 supports. a. nonconduc'ting block .2112 carryin ..a.ball bearingZB. .Bearings '21 .andf28 support an 5 armature'shaft 29 carrying a core 30,, .windings 3| and the commutator.32. Reierring'toiFigflo, commutator .32 .engages by brushes -33 and 34 guided by metal boxes 35 attached by screws-35a itothe .block 21a. .Spring 36 urges the brushes against the commutator.

.The shell'Z l, plate'.24, and block TM are maintained .in assembled relation .by thru bolts 40 cooperatingwith nuts M and 42. Nut' ll serves .alsolto retain a plate 43 located against thesleeve 4'4 whichis located against the block 21a and is received by arecess'therein. Nut 42 on the upper "thru bolt 40 .(Figi'3) .retainsahub 45 and a second spacer .sleeve 44 against the plate 4.3. .A nut '46 .cocperat.es with .the upper thru bolt 4llto 2o retain-a cover 4.1,foramagnetically controlled brake.

Referring to Fig. 9, the'brakecomprises a brake .disc attached to.shaftj29 and a brake. shoe 5| having itsfixed end portionsecuredto v.the hub 45. A spring52, connecting the free .end portion of the shoe 5| witha lug "513 integral with .plate '43, urgesthe shoe "5| against the brakedisci50. The shoe'5l is magnetizable and provides the armature :of .an electromagnetcomprising a coil "surrounding a core'56 attachedto an ear 51integral with-plate 43. When the motor. is connected with a current source,:the coil 55.is energized and .causesthe .bra'ke shoe 5| to.be attracted 'awayirom the brake 'disc*50.

The gear reduction unit is shown in Figs. 6, 7 and-8. It comprises parallel bearing supporting plates and 'BI which are maintained. in spaced "relation by, four'spacing studs '62 (Fig. '3) having their 'leftendsrattached at 62a. to' the plate -6'l and havingtheir right ends 62b threaded and passed thru holesinthe plate'60. Nuts 620.cooperate with the'threaded ends 62b to hold the plate 60 against the shoulders 62d provided by the studs '62. The plates -66 and "6 I support LfiVe 'pairsof alignedbearings 63.having spherical outer surfaces received-by spherically formed recesses -64 in th plates 60 and -6 l 'and by spherical'formed flanges 55 provided by retainer plates Y 66 attached by rivetsfil tothe-plates 60 and'Bl.

The end plate -26 of the electric motor .20 isattached to the plate 60 by screws '68 ('Fig. 9) 'receivedby tapped holes-'69 (Fig. .6) in the -plate 60. Motor armature shaft .29 .drives ...a pinion Tllmeshing with 'a gear H connected with 55 shaft'l2 providing a pinion'lB meshing witha gear '14 fixed :to a shaft 15 providing a. pinion l6. meshing 'with a. gear 11 .fixed to a shaft"!!! providing a pinion l9 meshing with agear .80

connected with .arsha'ft' '81 providing .a pinion--82 60 meshing withia ,gear 82 connected with.a shaft 84 providing a pinion 85 meshing with a gear 86 fixed to a shaft 81 supported by ball bearings 88 and 89 provided, respectively, by the plates 60 and 6|.

Referring to Fig. 3, a housing 90, which is generally circular in formation as shown in Fig. 4, is provided with a partition wall 9I dividing the interior of the housing 90 into a compartment 92 for receiving the speed reducing gearing unit and a compartment 93 for receiving limit switches as shown in Fig. 4 or to receive limit switches and a centering switch as shown in Fig. 11. The housing 90 is oounterbored at 90a (Fig. 3) to receive the plate 60, and is counterbored at 90b to receive the plate 6|. Screws 9Ia (Fig. 4) extend through the partition 9| and are threaded into tapped holes 9Ib in plate BI (Fig. 7). The tightening of the screws 9Ia causes plate 60 to be drawn against the annular ledges of the counterbore 90a The boss 89a (Fig. 8) surrounding the ball bearing 89 extends thru a hole in the partition 9| as shown in Fig. 12. The shaft 81 extends thru the chamber 93 and thru an opening in a cover plate 95 attached by screws 96 to the partition 9|. Fig. 4 shows threaded holes 96a for receiving the screws 95.

Exterior to the cover 95 the shaft 81 is provided with a key I connecting shaft 81 with a sleeve IOI which provides the hub of a clutch disc I 02. A second clutch disc I03 is splined to the hub IOI. Between the two discs I02'and I03, there is located the hub I04 of a lever I05 having clutch facings I06 and I01 attached thereto. Pressure between the clutch parts is applied by a spring I08 located between the disc I03 and the flange I09 of a cupped washer IIO retained by a nut I I I and a lock washer II2 cooperating with the sleeve IOI. Sleeve IN is retained on shaft 81 by a nut II3 threadedly engaging the shaft and retained by a lock washer 'I I4. The spring I08 is so adjusted as to provide a friction clutch connection between the shaft 81 and the arm I05 such as to transmit the torque required to operate an apparatus connected with the arm However the friction between the clutch parts should not be so great as to prevent operation of the lever I05 manually.

Lever I05 carries a pin I20'which is received selectively by one of several notches I2I in the flange I22 of a disc I23 (Fig. 3) attached to a sleeve I 24 loosely journalled on shaft 81 and splinedly connected with a nonconducting hub I 25. In Fig. 5 the splines of sleeve I24 are shown at I24a and the splines of hub I25 at [2511, This spline connection provides for connecting the hub I24 with the hub I25 after the cover 95 has been attached. I

Referring also to Fig. 4, the hub I25 carries the metallic segment I26 of a limit switch which includes brushes I21, I28 and I29 guided by boxes I30 attached to a nonconducting plate I3I which is centrally apertured to clear the hub I25.

Springs I30a urge these brushes against the segment I26. Plate I3I has arcuate edges I32 received by arcuate shoulders I33a of bosses I33 provided by partition 9|. In Fig. 4, the upper bosses I33 show the arcuate shoulders I33c. These shoulders are defined by an arc coaxial with shaft 81, By moving a handle I31 attached thereto, the plate I3I can be rotated around the shaft 81 to adjust the brushes I21, I28 and I29 relative to the segment I26. The plate I3I is retained in adjusted position by tightening screws I34 threaded into holes I34a in bosses I33 to force plates I36 against the plate I3I. Plates I36 are prevented from rotating by the studs I35 attached thereto which are received by holes I35a in the bosses I33.

In the modification shown in Figs. 11 to 13, the operating lever I05 is directly keyed at I 00 to shaft 81', the friction clutch being omitted. Lever I05 has a split hub I01 which is forced against the shaft 81 by a screw I08 and a nut I09. Shaft 81 is connected by key I4I with a sleeve I40 to which an insulated hub I25 is bonded. Hub I25 carries the segment I26 of the limit switches which are the same in construction as the form shown in Figs. 3 and 4. Sleeve I40 provides the hub of a gear I42 which drives a gear I43 having a hub I44 journalled on a stub shaft fixed to partition 9I. Hub I44 is bonded to an insulating hub I46 carrying metal segments I41 and I48 engaged by brushes I49 and I50, respectively, which are supported by brush holders I5I attached to a nonconducting plate I53 and which are urged by springs I52, against the metal segments. The segments I41 and I48 are engageable with a contact I60 integral with ears IfiI pivoted on a stud I62 attached to the plate I53 which is supported in the same manner as the plate I3I below. Plate I53 has an adjusting handle I54. A spring I60, connecting an ear I6I and a stud I64 fixed to plate I3I, urges contact I6I toward the hub I46.

Fig. 14 is the wiring diagram for the modification shown in Figs. 11 to 13. The motor brushes 33 and 34 are connected, respectively, with armatures I13 and I14 of relays HI and I12. Springs I13a and I140; are normally efiective to urge the armatures I 13 and I14, respectively, toward the left to cause contacts I15 and I16, respectively, supported by these armatures, to engage contacts I11 and I18, respectively. By magnetic attraction, the armatures I13 and I14 can move to the right to separate contacts I15 and I16, respectively, from contacts I11 and I18 and cause contacts I19 and I to engage contacts I 8| and I82 respectively. The magnets of the relays HI and I12 are provided, respectively, by coil I83 on a core I85 and by coil I84 on a core I86.

Wires I81 and I88,connect contacts I8I and I82, respectively, with wire I89 connectible by a switch I 90 with a battery I9I connected by wire I92 with a switch I93 with centering-switch brush I60. Brake control magnet coil 51 is connected between wire I92 and a wire I94 connected with relay contacts I11 and I18. A variable resistance 231' and motor field 23 are connected between wires I92 and I94. Limit-switch brush I29 is connected with relay coil I83 connected with a wire I95 leading to centering switch brush I 49. A switch I91 connects wires I92 and I95. Limitswitch brush I21 is connected with relay coil I84 connected with a wire I98 leading to centeringswitch brush I50. A switch I98 connects wire I98 with a wire I99 connected with wire I92.

Switch I90 is closed before operation of the motor in either direction can take place. Switches I 91, I98 and I93 are selectively operated by direct manipulation or. by remote control. When switch I91 is closed, relay IN is effective to cause current to flow through the motor armature 3! in a direction such that hub I25 rotates clockwise until the switch I91 is opened but not after segment I28 leaves the brush I29. When switch I98 is closed, relay I12 is effective to cause current to flow through the motor armature 3| in a direction such that hub I25 rotates counterclockwise until the switch I98 is opened but not after segment I26 leaves the brush I21. When switch I93 is closed, the motor operates in the direction required to bring the arm I05 back to center position. When either one of the switches I93, I91 and I98 is closed and either one of the relays I1I, I12 is energized, the brake magnet coil 51, as well as the motor field 23, is energized to cause the brake shoe 5I to move away from the brake drum 50. When the relays are disconnected from the battery either by the opening of the limit switches or the centering switch or by opening any of the switches I93, I91 and I98 which had been previously closed, the relays are deenergized and likewise the magnet coil 51 whereupon the spring 52 is efiective to cause the brake shoe 5| to engage the brake drum 50.

The wiring diagram of the first form of the electric servo-motor unit is the same as shown by Fig. 14, but with the centering-switch, wires I95 and I90 and switch I93 omitted. The relays Ill and I12 which are used with both forms are supported by a plate 200 attached to gear case 90 by screws 20I (Fig. 4) and are enclosed by'a cover 202. Screws 203 (Fig. 4) attach to case 90 a plate 204 supporting junction blocks 205 and the resistance 231. These parts are enclosed by a cover 206 attached to plate 204 by a stud 201 and a nut 208. Various connections shown diagrammatically in Fig. 14 are made within the enclosure provided by plate 204 and cover 206.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What is claimed is as follows:

1. An electric servo-motor unit comprising a frame providing a gear housing open at one end, said frame having a wall closing the other end of the gear housing, a subassembly comprisin a train of speed reducing gears and spaced parallel plates by which the gears are supported, one of the plates being attached to said wall of the frame and the other plate providing a cover for the gear compartment of said housing and having an opening providing access to the first gear of the speed reducing train, a sub-assembly comprising an electric motor having a frame and an armature shaft extending from the frame and a gear attached to the armature shaft, means for so attachin the motor frame to the second mentioned plate of the gear sub-assembly that the gear on the motor armature shaft meshes wtih the first gear of the gear train and the motor frame covers the hole in the second mentioned plate, and an operating member driven by the gearing.

2. In a device of the character described, the combination with a cup-shaped housing having an opening in its bottom wall; of a unitary subassembly adapted to be secured to said housing and comprising two discs rigidly held together in parallel spaced relation and adapted to be telescopically received by the cup-shaped housing so that the one disc rests upon the bottom wall of said housing and the other disc forms a cover plate for the open end of the cup-shaped housing, a plurality of shafts journalled in and between said discs and having cooperating gears forming a speed reducing gear train, one of said shafts extending through the opening in the bottom wall of the housing, an electric motor secured to the cover disc and having its shaft 0peratively connected with a shaft of the speed reducing gearing to drive it; and means for securing the two discs to said housing.

motor, are supported, the plate to which the motor is secured fitting into the open end of the frame to form a cover therefor and the other plate resting upon and secured to the partition to fasten the sub-assembly to the frame; a shaft driven by the speed reducing gearing, extending through the aperture in the partition into the other compartment adjacent the one containing the gearing; a cover for the said other compartment, said cover having an opening through which the shaft extends; a switch mechanism in the said other compartment operative by the shaft; and an operated lever secured to the shaft outside the cover for said other compartment.

4. An electric servo motor unit comprising a frame providin a gear housing open at one end, said frame having a wall closing the other end of the gear housing and having a hole therein; a unitary sub-assembly adapted to be assembled with the housing and comprising a speed reducing gear train and an electric motor for driving the gear train and an operating shaft driven by the gear train and extending through said hole, the unitary sub-assembly having means cooperating with the frame adJacent its open end to provide a cover therefor when the gear train is located within the housing; and means for securing the sub-assembly to the wall of the frame.

5. An electric servo motor unit comprising a unitary sum-assembly having spaced, coaxially aligned discs; an electric motor attached to one of said discs; a train of speed reducing gearing supported between said discs and operatively connected to the electric motor; shafts carrying said gearing and holding the discs in spaced relation; a frame having an open end into which the discs are inserted to house the gearing, said open end having an annular recess providing a ledge upon winch the motor supporting disc seats, said also forming a cover for the frame; an annular recess in the frame for receiving the disc in coaxial alignment with the motor supporting disc; means for securing the sub-assembly to the frame; and an operating arm driven by the gearing.

6. An electric servo motor unit comprising a tubular housing having a partition wall intermediate its open ends; a unitary sub-assembly comprising two annular, coaxial, spaced discs, shafts between said discs, certain of which support cooperating gears of a spaced reducing gear train, the others holding the discs properly spaced, an electric motor attached to the one disc and operatively connected to the gear train; coaxial, annular recesses in the open end of the housing and the partition wall, the recess in the open end receivin the motor supporting disc, the recess in the partition wall receiving the other disc; means in the partition wall for securing the seating disc of the sub-assembly thereto; a shaft extending from the gear train through an opening in the partition wall; a switch for controlling the motor, secured in the housing on the side of the partition wall opposite the gear train; means on the shaft for actuating the switch; and a lever on the shaft operated thereby.

ROBERT H. HILL. 

